The invention relates generally to 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) Self-Optimizing Networks. More specifically, the invention relates to traffic engineering systems and methods that efficiently adjust multimedia Internet Protocol (IP) networks to evolving traffic load patterns and growth.
A multimedia IP network must accommodate traffic flows having different characteristics, Quality of Service (QoS) and Per Hop Behavior (PHB) requirements. These three aspects are the Service Level Specification (SLS) which is the technical specification of the service level being offered by a Service Provider to a Subscriber. The number of SLSs may vary from 1 to 16 depending on customer application requirements. The varying SLSs in multimedia networks are difficult to satisfy without traffic segregation into classes and the corresponding network bandwidth partitioning.
Metro Ethernet Forum (MEF) Technical Committee specification 10.1 provides the definition and scope of traffic management mechanisms and parameters for Ethernet services. This helps the Service Provider and its Subscriber to mutually agree on an SLS associated with a given service instance. In particular, MEF 10.1 specifies a common way for specifying bandwidth profiles and performance definitions. The bandwidth profile includes a set of traffic parameters and rules for the disposition of each Service Frame based on its level of compliance with the Bandwidth Profile parameters.
The performance definitions are a set of service performance metrics in terms of Frame Delay, Frame Delay Variation, and Frame Loss Ratio that are useful in aligning a service with the application that will use it. The parameters comprising the Bandwidth Profile parameters are: 1) Committed Information Rate (CIR) expressed as bits per second (bps). The CIR must be greater than 0. 2) Committed Burst Size (CBS) expressed as bytes. When the CIR is greater than 0, the CBS must be greater than or equal to the maximum Service Frame size as specified. 3) Excess Information Rate (EIR) expressed as bps. The EIR must be greater than 0. 4) Excess Burst Size (EBS) expressed as bytes. When the EIR is greater than 0, the EBS must be greater than or equal to the maximum Service Frame size as specified. 5) Coupling Flag (CF). 6) Color Mode (CM). Each incoming Service Frame is classified to determine which, if any, Bandwidth Profile is applicable to the Service Frame. Operation of the Bandwidth Profile algorithm is governed by the above six parameters, CIR, CBS, EIR, EBS, CF and CM. An algorithm declares Service Frames as compliant or non-compliant relative to the Bandwidth Profile parameters. The level of conformance is expressed by one of three colors; green, yellow or red. The Bandwidth Profile algorithm is in color aware mode when each incoming Service Frame already has a level of conformance color associated with it and that color is taken into account in determining the level of conformance to the Bandwidth Profile parameters.
MEF 10.1 is compatible with the Internet Engineering Task Force (IETF) Differentiated Services (DiffServ) Traffic Engineering (TE) framework. The DiffServ framework is aimed at providing a way of setting up QoS using policy statements that form part of a service level agreement between a service user and a network operator. The policy may use several IP packet header fields to classify the packet, but the classification marking can also be a simple identifier within the packet header. DiffServ codepoints are used to identify packets that should have the same aggregate PHB with respect to how they are treated by individual network elements within the network. Furthermore, DiffServ Codepoints (DSCPs) may be mapped into Ethernet (p) bits. To support the DiffServ model, the IETF has released the Russian Dolls Model (RDM) and Maximum Allocation Model (MAM) bandwidth management drafts.
Voice, data, and video traffic may be assigned to either one of two broad traffic categories, real-time (streaming) or elastic. Real-time packets need to be delivered in a timely manner with packet delay and delay variation being the most important quality measures. If a voice packet is not delivered within the required time constraints, it is considered not useful by the upper layer protocols and will be discarded. Real-time traffic is usually generated by real-time applications such as audio/video communications. The Expedited Forwarding (EF) PHB is used to provide a low loss, low delay, and low jitter end-to-end service across a DiffServ domain for this traffic.
Real-time streaming traffic is open-loop controlled, with rate and duration as intrinsic characteristics. From the end user standpoint, the main QoS indicators are negligible service request rejection (low blocking) as well adequate transmission quality (low delay and low jitter).
Applications that generate elastic traffic require reliable packet delivery. Every piece of data needs to be transferred, and in case of packet losses the respective packets are retransmitted. In terms of QoS, emphasis is on user perceived throughput, usually averaged for the length of the session. Per-packet delay and delay jitter are unimportant as long as the total amount of data is delivered within a certain period of time. The most popular applications in this category are Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP). They are based on the Transmission Control Protocol (TCP)/TP protocol which offers reliable data transfer. TCP employs feedback control mechanisms to adapt the transfer rate to current network conditions that allow traffic on one link to share available capacity.
Elastic traffic is closed-loop controlled, with average rate and download time as the measures of performance. The main QoS indicator from the end user standpoint is adequate response time (directly proportional to average throughput in kbps or Mbps) in seconds.
This results in a natural division of a network into service classes. For example, for IP networks based on Ethernet technology, it is possible to define separate Ethernet Virtual Connections (EVCs) for each service class. Furthermore, wireless network operators' current engineering practices are to segregate real-time streaming traffic into conversational (class A) and IP Multimedia Subsystem (IMS) traffic (class B). Elastic traffic is segregated into buffered streaming (class C) and TCP/IP based WEB applications (class D). A given traffic class could require more than one EVC if the traffic justified it. The conversational class is reserved for “carrier grade” premium voice services, the IMS class applications are based on the UDP/IP protocol and the application could adapt to the network load conditions at the expense of quality degradation, the buffered streaming class is based on TCP/IP which provides a traffic flow regulation mechanism and class D is reserved for best effort (BE) applications.
One challenge in IP network traffic engineering has been to devise a bandwidth computation methodology to size the bandwidth allocated to each service class to efficiently accommodate different QoS requirements. While total network traffic may change relatively slowly over time, the per-class traffic mix may fluctuate both with time and destination. For example, in 3G mobile phone cellular networks, the traffic shifts as the mobile user negotiates the cellular region, from home to work and back. Also, mobile users generate mainly voice traffic, while home/work users access Internet applications. Given the number of network routing nodes, manual network reconfiguration is impracticable.
To date, automated methods that calculate bandwidth profile parameters that take into account per-traffic class SLSs have eluded network engineers as well as network operation centers. Current practices for IP networks rely on over-provisioning a single bandwidth partition (class) to ensure ad-hoc guarantees. For real-time streaming traffic, the over-provisioning ratio is typically 4:1 (25% efficient), and for elastic traffic, 2:1 (50% efficient).
The current generation of IP routers that are compliant with IETF DiffServ-TE, MEF specifications MEF 6, MEF. 10.1, MEF 11 or IEEE PBB/PBT/PLSB frameworks support traffic class separation as well as bandwidth partitioning. For the purpose of discussion, routers sometimes referred to as carrier-grade routers will be denominated switch-routers. Switch-routers also support the RDM and MAM bandwidth management models.
A multimedia IP network must efficiently support many multimedia applications using a fixed set of service categories to support various SLSs and end user bit rate requirements.
There exists a need for a traffic engineering method that can accommodate increasing service demands without unreasonable and unpredictable investment in network infrastructure.